Ghali Michael George Zaki
Department of Neurobiology and Anatomy, Drexel University College of Medicine, 2900 Queen Lane, Philadelphia, PA 19129, USA. Tel.: +1 703 577 4848; Fax: +1 703 933 3837; E-mail:
J Integr Neurosci. 2017;16(2):189-208. doi: 10.3233/JIN-170010.
The sympathetic nervous system maintains and regulates arterial pressure and tissue perfusion, via control of cardiac output and vasomotor tone. Sympatho-vascular-mediated increases in blood pressure are effected by arterioloconstriction, which causes an increase in afterload, and/or venoconstriction, which increases venous return, left ventricular preload, and consequently, the force of cardiac contraction via Frank-Starling mechanisms; withdrawal of sympathetic drive elicits reciprocal effects. Spinalization reduces mammalian arterial pressure to 40-50 mm Hg consequent to the elimination of descending medullary pre-sympathetic bulbospinal drive to preganglionic sympathetic fibers in the intermediolateral cell column of the spinal cord. Beyond agreement that sympathetic tone is generated supraspinally, there is only controversy. One hypothesis posits that pre-sympathetic medullary regions, such as the rostral ventrolateral medulla (RVLM) and caudal raphé group, possess intrinsic tonic activity. Alternatively, pre-sympathetic medullary regions may receive tonic excitation from other areas in the brainstem. Neurons in the lateral tegmental field (LTF), an exclusively propriobulbar entity (cf. pre-Bötzinger complex - the propriobulbar inspiratory rhythmogenic kernel of the respiratory network), fire before and project to pre-sympathetic units in RVLM and caudal raphé and exhibit activity correlated to the cardiac-related rhythm in sympathetic nerve discharge, making the LTF a likely candidate for the primary source of basal sympathoexcitation. The LTF is additionally involved in a variety of cardiovascular and sympathetic reflexes (i.e., baroreflex, Bezold-Jarisch reflex). As it receives descending afferents from the infralimbic cortex and associated limbic structures, suggesting a role in the sympathetic response to fear, as well as vestibular inputs, consistent with a role in coordinating the sympathetic response with emesis proper, the LTF appears to play an extensive integrative role. In this review, we discuss the LTF, a once mysterious, poorly-characterized, and ill-defined region, the contribution of which to cardiovascular reflexes and basal sympathoexcitation has been more thoroughly elucidated in recent years and any model of central control of sympathetic output must take into consideration the contribution of this important region.
交感神经系统通过控制心输出量和血管运动张力来维持和调节动脉血压及组织灌注。交感神经 - 血管介导的血压升高是由小动脉收缩引起后负荷增加和/或静脉收缩增加静脉回心血量、左心室前负荷，并进而通过Frank-Starling机制增强心脏收缩力来实现的；交感神经驱动减弱则会产生相反的效果。脊髓横断会使哺乳动物的动脉血压降至40 - 50毫米汞柱，这是由于消除了延髓下行的节前交感神经驱动，该驱动通过脊髓中间外侧细胞柱中的节前交感纤维传导。除了大家都认同交感神经张力是由脊髓以上部位产生的之外，其余观点都存在争议。一种假说认为，节前交感神经髓质区域，如延髓头端腹外侧区（RVLM）和尾侧中缝核群，具有内在的紧张性活动。另一种观点则认为，节前交感神经髓质区域可能接受来自脑干其他区域的紧张性兴奋。外侧被盖区（LTF）中的神经元，它是一个仅存在于脑桥内部的结构（参照前包钦格复合体 - 呼吸网络的脑桥内部吸气节律产生核心），在RVLM和尾侧中缝核的节前交感神经单位之前放电并投射到这些单位，并且其活动与交感神经放电中的心脏相关节律相关，这使得LTF可能是基础交感神经兴奋的主要来源。此外，LTF还参与多种心血管和交感神经反射（即压力感受性反射、贝佐尔德 - 雅里什反射）。由于它接受来自边缘下皮质和相关边缘结构的下行传入纤维，提示其在对恐惧的交感反应中发挥作用，以及接受前庭输入，这与它在协调交感反应与呕吐本身方面的作用一致，所以LTF似乎发挥着广泛整合作用。在本综述中，我们将讨论LTF，这个曾经神秘、特征描述不佳且定义不明确的区域，近年来其对心血管反射和基础交感神经兴奋的贡献已得到更深入的阐明，并且任何关于交感神经输出中枢控制的模型都必须考虑到这个重要区域的贡献。
